(i) Field of the Invention
The present invention relates to a novel ultra high temperature lubricant composition. It also relates to a process for improving the performance of adiabatic diesel engines. More particularly, it relates to specific blends of (A) polyol esters; (B) triaryl phosphate esters; and (C) crankcase additive systems.
(ii) Prior Art
This paragraph summarizes the nature of the prior art without indentifying the specific documents, etc. The prior art discloses each of the three individual liquid components that may be blended together to form the blends of the present invention shown in all the Examples of the invention below. However, the prior art does not appear to disclose any specific blend comprising at least some of all three components. Thus, polyol esters (hereinafter "A"), triaryl phosphate esters (hereinafter "B"), and additive systems in mineral oil (hereinafter "C"), are all, individually, old in the art. The prior art also discloses lubricants that have been formed from A/B blends and crankcase lubricants formed from A/C blends. However, the known prior art does not contain any working examples of A/B/C blends. Even less does the prior art recognize critical ranges therein for ultra high temperature lubricants. Further, the prior art does not appear to contain any working examples of an A/B blend comprising B within the range from 20 to 60 weight percent. Nowhere does the known prior art disclose a crankcase lubricant that operates satisfactorily in newly developed diesel engines that operate without any forced cooling system at temperatures in excess of 1000.degree. F., and "approach adiabatic" conditions. For the purpose of this specification the term "adiabatic" is broadly defined to include "approaching adiabatic".
Specific items of prior art are now discussed in the following paragraphs.
Engines are now being developed which have operating temperatures within the range 1000.degree.-2500.degree. F. For example, see "The Amazing Ceramic Engine Draws Closer" by John W. Dizard at pages 76-79 of "Fortune", July 25, 1983. The article focuses on the use of ceramic parts, but says little about how such engines are lubricated.
Lubrication problems of adiabatic engines have been briefly discussed in Stauffer Chemical Company's Technical folder "Stauffer's New SDL-1.TM.". Under the section headed "High Temperature Operation" concerning adiabatic diesel engines, the following is stated:
" . . . This new engine development has been frustrated to some extent by the poor stability of standard mineral oil based lubricants. Attempts to satisfy the engine with synthetic hydrocarbon products also proved unsucessful. Stauffer SDL-1 was the only lubricant to function satisfactorily in this very high temperature environment."
Stauffer's Technical folder also notes that the lubricant used comprised a 100% polyol ester base (containing no diesters or snythetic hydrocarbons). In addition it comprised about 10% by weight of a mineral oil additive system similar to component C used in the examples of the invention hereinafter. Accordingly it was a lubricant of the A/C type.
Triaryl phosphate esters (i.e. component B of the invention) have been used for many years, in lubrication of air compressors and industrial gas turbines, and in a variety of hydraulic systems where fire-resistance is required.
Disclosures of A/B blends include those found in U.S. Pat. No. 3,992,309 (Dounchis); and in U.S. Pat. No. 4,440,657 (Metro).
Dounchis' claims 8-11 are of interest to the present invention. However, Dounchis does not appear to have any working example directed to any A/B blend wherein the volume percent of B is less than 65% as shown in Dounchis' Example V.
Metro discloses an A/B blend wherein B is present in an amount of up to 5% by weight. It is believed that Metro (filed 1982) implicitly contains negative teachings relative to the present invention.
U.S. Pat. No. 4,362,634 (Berens, assigned to Stauffer Chemical Company) is of interest in that it relates to an A/B/"D" blend wherein D is a specific surfactant and the components are present in the weight percent ranges (60-90)/(1-10)/(5-30). However the blend is used in aqueous emulsions as a metal working lubricant and has only a very low viscosity.
In sum, essentially the prior art does not disclose any working example of any blend which comprises B within the range of from above 10% to below 65%. Even less does the prior art recognize the existence of the criticality of a narrow range of 20 to 50 weight percent of B, when a third component C is present.